Dispenser for liquid crystal display panel and method for controlling gap between substrate and nozzle using the same

ABSTRACT

A dispenser for a liquid crystal display panel includes a syringe having a nozzle provided at an end thereof, a body in which the syringe is mounted, a vertical driving stepping motor for moving the body in a vertical direction, a first sensor for detecting whether the nozzle of the syringe is in contact with a substrate, a second sensor for detecting a gap distance between the nozzle and the substrate, and a main unit for controlling the vertical driving stepping motor in response to an output from the second sensor to obtain a desired gap distance between the nozzle and the substrate.

This application claims the benefit of the Korean Application No.P2002-081439 filed on Dec. 18, 2002, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dispenser for a liquid crystaldisplay panel and a method for controlling a gap distance between anozzle and a substrate when using the dispenser, and more particularly,to a dispenser for a liquid crystal display panel and a method forcontrolling a gap distance between a nozzle and a substrate when usingthe dispenser to control a gap distance between the substrate, where aliquid crystal display panel is formed, and the nozzle.

2. Discussion of the Related Art

In general, a liquid crystal display device is a display device wheredata signals according to picture information are individually suppliedto liquid crystal cells arranged in a matrix form. Light transmittanceof the liquid crystal cells is controlled in accordance with the datasignals to display a desired picture. The liquid crystal display deviceincludes a liquid crystal display panel where the liquid crystal cellsare arranged in a matrix form, and a driver integrated circuit (IC) fordriving the liquid crystal cells. The liquid crystal display panelincludes a color filter substrate and a thin film transistor arraysubstrate attached to each other. The liquid crystal display panelfurther includes a liquid crystal layer between the color filtersubstrate and the thin film transistor array substrate.

Data lines and gate lines are formed on the thin film transistor arraysubstrate of the liquid crystal display panel and cross each other atright angles so as to define liquid crystal cells. The data linestransmit a data signal supplied from the data driver integrated circuitto the liquid crystal cells. The gate lines transmit a scan signalsupplied from the gate driver integrated circuit to the liquid crystalcells. At an end portion of each of the data lines and the gate lines, adata pad and a gate pad are respectively provided in which data signalsand scan signals are respectively applied from the data driverintegrated circuit and the gate driver integrated circuit. The gatedriver integrated circuit sequentially supplies a scan signal to thegate lines so that the liquid crystal cells arranged in a matrix formcan be sequentially selected line by line while a data signal issupplied to the selected line of the liquid crystal cells from the datadriver integrated circuit.

A common electrode and a pixel electrode are respectively formed on theinner side of the color filter substrate and the thin film transistorarray substrate for applying an electric field to the liquid crystallayer of a liquid crystal cell. More particularly, a pixel electrode isrespectively formed in each liquid crystal cell on the thin filmtransistor array substrate, while the common electrode is integrallyformed across the entire surface of the color filter substrate.Therefore, by controlling a voltage applied to the pixel electrode whilea voltage is applied to the common electrode, light transmittance of theliquid crystal cells can be individually controlled. To control thevoltage applied to the pixel electrode by liquid crystal cells, a thinfilm transistor is formed in each liquid crystal cell and used as aswitching device.

FIG. 1 is a plane view of the unit liquid crystal display panel formedby a thin film transistor array substrate and a color filter substrateaccording to the related art. As shown in FIG. 1, the liquid crystaldisplay panel 100 includes an image display part 113 where the liquidcrystal cells are arranged in a matrix form, a gate pad part 114connected to the gate lines of the image display part 113, and a datapad part 115 connected to the data lines of the image display part 113.The gate pad part 114 and the data pad part 115 are formed along an edgeregion of the thin film transistor array substrate 101, which does notoverlap with the color filter substrate 102. The gate pad part 114supplies a scan signal from the gate driver integrated circuit to thegate lines of the image display part 113, and the data pad part 115supplies image information from the data driver integrated circuit tothe data lines of the image display part 113.

Data lines to which image information is applied and gate lines to whicha scan signal is applied are provided on the thin film transistor arraysubstrate 101. The data lines and the gate lines cross each other.Additionally, a thin film transistor for switching the liquid crystalcells is provided at each crossing of the data lines and the gate lines.A pixel electrode for driving the liquid crystal cells is connected tothe thin film transistor and provided on the thin film transistor arraysubstrate 101. A passivation film for protecting the pixel electrode andthe thin film transistor is formed at the entire surface of the thinfilm transistor array substrate 101.

Color filters are provided on the color filter substrate 102 for eachcell region. The color filters are separated by a black matrix. A commontransparent electrode is also provided on the color filter substrate102.

A cell gap is formed by a spacer between the thin film transistor arraysubstrate 101 and the color filter substrate 102. A seal pattern 116 isformed along an outer edge of the image display part 113. The thin filmtransistor array substrate 101 and the color filter substrate 102 areattached by the seal pattern 116 to thereby form a unit liquid crystaldisplay panel.

In fabricating the unit liquid crystal display panel, a method forsimultaneously forming unit liquid crystal display panels on alarge-scale mother substrate is generally used. Thus, a process isrequired for separating the unit liquid crystal display panels from thelarge-scale mother substrate. For example, a cutting process can be usedon the mother substrate to separate the plurality of unit liquid crystaldisplay panels formed thereon.

The seal pattern 116, as discussed above, has an opening. After the unitliquid crystal display panel is separated from the large-scale mothersubstrate, liquid crystal is injected through a liquid crystal injectionopening to form a liquid crystal layer at the cell-gap, which separatesthe thin film transistor array substrate 101 and the color filtersubstrate 102. Then, the liquid crystal injection opening is sealed.

As mentioned above, the following steps are required to fabricate theunit liquid crystal display panel: the thin film transistor arraysubstrate 101 and the color filter substrate 102 are separatelyfabricated on the first and second mother substrates, the first andsecond mother substrates are attached in such a manner that a uniformcell-gap is maintained therebetween, the attached first and secondmother substrates are cut into unit panels, and then liquid crystal isinjected to the cell-gap between the thin film transistor arraysubstrate 101 and the color filter substrate 102. In particular, theprocess of forming the seal pattern 116 along an outer edge of the imagedisplay part 113 is required to attach the thin film transistor arraysubstrate 101 and the color filter substrate 102. The related artprocess of forming a seal pattern will now be described.

FIGS. 2A and 2B illustrate a screen printing method to form a sealpattern. As shown in FIGS. 2A and 2B, there is provided a screen mask206 patterned so that a of seal pattern forming region is exposed. Arubber squeegee 208 is used to selectively supply a sealant 203 to thesubstrate 200 through the screen mask 206 so as to simultaneously form aseal pattern 216. The seal pattern 216 formed on the substrate 200creates a gap in which liquid crystal layer is later injected andprevent leakage of the liquid crystal. Thus, the seal pattern 216 isformed along each outer edge of the image display part 213 of thesubstrate 200 and liquid crystal injection opening 204 is formed for theseal pattern 216.

The screen printing method includes: applying the sealant 203 on thescreen mask 206 with the seal pattern forming region patterned thereon,forming the seal pattern 216 on the substrate 200 through printing withthe rubber squeegee 208; and evaporating a solvent contained in the sealpattern 216 and leveling the pattern. The screen printing method iswidely used because it is an easy process. However, the screen printingmethod is disadvantageous in that sealant 203 is wasted because a lot ofsealant is discarded after the squeegee 208 is drawn across the screenmask to form the seal pattern 216. In addition, the screen printingmethod has a problem in that rubbing of an orientation film (not shown)formed on the substrate 200 can incur defects when the screen mask 206and the substrate 200 come into contact with each other. These defectswill degrade picture quality of the liquid crystal display device.

To overcome the shortcomings of the screen printing method, a sealdispensing method has been proposed. FIG. 3 is an exemplary view of arelated art dispensing method for forming a seal pattern. As shown inFIG. 3, while a table 310 with the substrate 300 loaded thereon is movedin forward/backward and left/right directions, a seal pattern 316 isformed along an outer edge of image display part 313 on the substrate300 by applying a predetermined pressure to syringe 301 filled with asealant. The seal pattern 316 is sequentially formed for the imagedisplay part 313.

In the seal dispensing method, since the sealant is selectively suppliedto the region where the seal pattern 316 is to be formed, sealant wasteis prevented. In addition, the syringe 301 does not contact theorientation film (not shown) of the image display part 313 of thesubstrate 300 so that the rubbed orientation film will not be damaged.Thus, picture quality of the liquid crystal display device will bemaintained.

In the case of forming the seal pattern 316 on the substrate 300 byusing the syringe 301, a technique for precisely controlling a gapdistance between the substrate 300 and the syringe 301 is required. Thatis, if the substrate 300 and the syringe 301 are too close compared to adesired gap distance, the seal pattern 316 formed on the substrate 300is wide and thin. If, however, the substrate 300 and the syringe 301 areseparated too much compared to the desired gap distance, the sealpattern 316 formed on the substrate 300 becomes narrow and may becomenoncontiguous, which causes a defect in the liquid crystal displaydevice.

If the sealant in the syringe 301 is completely used up while forming aseal pattern, the seal pattern 316 cannot be completely formed. Thus, asyringe 301 should be replaced with another syringe 301 filled with thesealant before it is completely used up. At this time, however, the gapdistance between the substrate 300 and the syringe 301 varies dependingon the syringe 301 in use. Thus, the gap distance between the substrate300 and a syringe 301 should be reset and/or checked every time asyringe 301 is replaced with a new syringe. Replacement of the syringe301 is frequently done during actual manufacturing of products.Therefore, a technique for setting or checking the gap distance betweenthe substrate 300 and the syringe 301 within a short time is preferable.

In the related art, a manual operation method has been adopted tocontrol the gap distance between the substrate 300 and the syringe 301,which will now be described in detail. FIG. 4 is an exemplary viewshowing a seal dispenser of a liquid crystal display panel in accordancewith the related art. As shown in FIG. 4, a seal dispenser includes asyringe 403 with a nozzle 402 at one end thereof for supplying a sealantonto a substrate 401 that is loaded onto a table 400, a body 404 formounting the syringe 403 above the substrate 401, a vertical drivingservo motor 405 for moving the body 404 in a vertical direction; amicrogauge 406 for turning the vertical driving servo motor 405 viamanual operation, a first sensor 407 for detecting whether the substrate401 and the nozzle 402 are in contact with each other; and a secondsensor 408 for detecting a gap distance between the substrate 401 andthe nozzle 402.

FIG. 5 is a flow chart of a method according to the related art forcontrolling a gap distance between the nozzle and the substrate by usingthe seal dispenser of the liquid crystal display panel. As shown in FIG.5, the method according to the related art for controlling a gapdistance between the nozzle and the substrate by using the sealdispenser of the liquid crystal display panel includes lowering thenozzle 402 by manually manipulating the microgauge 406; detectingwhether the nozzle 402 and the substrate 401 are in contact with eachother; raising the nozzle 402 by manually manipulating the microgauge406; and stopping the nozzle at the gap distance between the nozzle 402and the substrate 401.

The related art of the seal dispenser of the liquid crystal displaypanel and the method for controlling a gap distance between the nozzleand the substrate using the dispenser will now be described in moredetail. First, when the substrate 401 is loaded on the table 400, a userturns the vertical driving servo motor 405 by manually manipulating themicrogauge 406 to thereby lower the syringe 403 mounted in the body 404.At this time, the user detects whether the nozzle 402 provided at an endportion of the syringe 403 and the substrate 401 loaded on the table 400are in contact with each other through monitoring of a value measured bythe first sensor 407.

When the substrate 401 and the nozzle 402 are detected to be in contactwith each other by the first sensor 407, the user turns the verticaldriving servo motor 405 by manually manipulating the microgauge 406,thereby raising the syringe 403 mounted in the body 404. At this time,the user detects whether the gap distance between the substrate 401 andthe nozzle 402 reaches a desired value through monitoring of a valuemeasured by the second sensor 408 and stops manipulating the microgauge406 when the value measured by the second sensor 408 reaches a desiredvalue.

The related art of the seal dispenser of the liquid crystal displaypanel and the method for controlling a gap distance between the nozzleand the substrate have the following problems. First, since the usercontrols the gap distance between the substrate 401 and the nozzle 402by manually manipulating the microgauge 406, reliability and consistencyare low, which increases the defective occurrence rate in themanufactured liquid crystal display panels. In addition, even a skilleduser requires a lot of time to set the gap distance between thesubstrate 401 and the nozzle 402 precisely, which degrades productivity.Furthermore, since the gap distance is set by the user's manualoperation, a strong and constant concentration, which quickly tiresusers, is required for users to maintain a good process pace.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a dispenser for aliquid crystal display panel and method for controlling gap betweensubstrate and nozzle using the same that substantially obviates one ormore of the problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a dispenser for aliquid crystal display panel and a method for controlling a gap distancebetween a nozzle and a substrate using the same that are capable ofautomatically controlling a gap distance between a nozzle provided at adispenser and a substrate.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a dispenser for a liquid crystal display panelincluding: a syringe having a nozzle provided at an end thereof; a bodyin which the syringe is mounted; a vertical driving stepping motor formoving the body in a vertical direction; a first sensor for detectingwhether the nozzle of the syringe is in contact with a substrate, asecond sensor for detecting a gap distance between the nozzle and thesubstrate; and a main unit for controlling the vertical driving steppingmotor in response to an output from the second sensor to obtain adesired gap distance between the nozzle and the substrate.

In another aspect, there is also provided a method for controlling a gapbetween a nozzle and a substrate using a dispenser for a liquid crystaldisplay panel including: lowering a body with a syringe mounted thereinusing a vertical driving stepping motor; detecting whether a nozzle ofthe syringe is in contact with a substrate; raising the body; detectinga gap distance between the nozzle and the substrate; and controlling thevertical driving stepping motor so that a desired gap distance isobtained between the nozzle and the substrate.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a plane view of the unit liquid crystal panel formed byattaching a thin film transistor array substrate and a color filtersubstrate according to the related art.

FIGS. 2A and 2B illustrate formation of a seal pattern through a screenprinting method in accordance with the related art.

FIG. 3 illustrates formation of a seal pattern through a seal dispensingmethod in accordance with the related art.

FIG. 4 illustrates a seal dispenser of a liquid crystal display panel inaccordance with the related art.

FIG. 5 is a flow chart of a method according to the related art forcontrolling a gap distance between a nozzle and a substrate using theseal dispenser of FIG. 4.

FIG. 6 illustrates a dispenser for a liquid crystal display panel inaccordance with an embodiment of the present invention.

FIG. 7 is a flow chart of a method in accordance with an embodiment ofthe present invention for controlling a gap distance between a nozzleand a substrate using the dispenser of FIG. 6.

FIG. 8 shows a detailed construction of a second sensor in FIG. 6.

FIG. 9 is a schematic view showing a sectional structure of one edge ofthe liquid crystal display panel.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to the illustrated embodiments ofthe present invention, examples of which are illustrated in theaccompanying drawings.

FIG. 6 illustrates a dispenser for a liquid crystal display panel inaccordance with the present invention. As shown in FIG. 6, a dispenserfor a liquid crystal display panel in accordance with the presentinvention includes a table 500 for supporting a substrate 501, a syringe503 with a nozzle 502 provided at an end portion thereof for supplying asealant onto the substrate 501, a body 504 in which the syringe 503 ismounted, a vertical driving stepping motor 505 for moving the body 504along a vertical shaft 506 in a vertical direction, a first sensor 507for detecting whether the nozzle 502 of the syringe 503 is in contactwith the substrate 501, a second sensor 508 for detecting a gap distancebetween the nozzle 502 and the substrate 501 and a control unit 509 forcontrolling the vertical driving stepping motor 505. The control unit509 controls the vertical driving stepping motor 505 based upon signalsfrom the first sensor 507 and the second sensor 508. The control unit509 can be located in the body 504, on an external surface of the body504, integrated into one of the sensors, integrated into both of thesensors or at a location completely separate from the body 504.

FIG. 7 is a flow chart of a method in accordance with an embodiment ofthe present invention for controlling a gap distance between a nozzleand a substrate using the dispenser of FIG. 6. As shown in FIG. 7, amethod for controlling a gap distance between a nozzle and a substrateusing the dispenser includes lowering the body 504 having the syringe503 mounted therein using the vertical driving stepping motor 505;detecting whether the nozzle 502 of the syringe 503 is in contact withthe substrate 501; raising body 504; detecting a gap distance betweenthe nozzle 502 and the substrate 501; and controlling the verticaldriving stepping motor 505 so that the gap distance between the nozzle502 and the substrate 501 obtains a desired gap distance.

The dispenser for a liquid crystal display panel and the method forcontrolling a gap distance between the nozzle and the substrate usingthe dispenser will now be described in detail. First, the substrate 501is loaded onto the table 500. The vertical driving stepping motor 505 isthen driven to lower the body 504 having the syringe 503 mountedtherein. After the body 504 is lowered, the first sensor 507 is used todetect whether the nozzle 502 provided at an end portion of the syringe503 is in contact with the substrate 501.

If the table 500 is metallic, a magnetic sensor, for example, can beused as the first sensor 507. The magnetic sensor in the body 504 sendsa signal to the control unit 509 that changes as the body 504 is loweredby the vertical driving stepping motor 505 toward the table 500. Whenthe nozzle 502 is in contact with the substrate 501, the lowering of thebody 504 stops so that the electric signal stops changing. The controlunit 509 recognizes an absence of change in the electric signal as thenozzle 502 being in contact with the substrate 501. When the controlunit 509 recognizes that lowering of the body 504 has stopped, thecontrol unit 509 stops the vertical driving stepping motor 505.

After the control unit 509 has controlled the vertical driving steppingmotor 505 to stop the lowering of the body 504, the control unit 509controls the vertical driving stepping motor 505 to raise the body 504.A second sensor 508 is used to detect the gap distance between thenozzle 502 and the substrate 501. Based upon an output from the secondsensor 508, the control unit 509 controls the vertical driving steppingmotor 505 to raise the body 504 so that a desired gap distance can beobtained between the nozzle 502 and the substrate 501. Subsequently, thecontrol unit 509 controls the vertical driving stepping motor 505 toraise and lower the body 504 so that a desired gap distance, can bemaintained between the nozzle 502 and the substrate 501. A laserdisplacement sensor, which has an accuracy, for example, of ±200 μm canbe adopted as the second sensor 508.

FIG. 8 shows a detailed construction of a second sensor of FIG. 6 inaccordance with an embodiment of the present invention. As shown in FIG.8, the laser displacement sensor is provided near the nozzle 502 of thebody 504, and includes a light emitting unit 508A irradiating laser onthe surface of the substrate 501 and a light receiving unit 508B onwhich the laser irradiated from the light emitting unit 508A is incidentafter being reflected from the substrate 501. The light receiving unit508B is constructed to detect a gap distance between the nozzle 502 andthe substrate 501 according to a position on the surface of the lightreceiving unit 508B at which the laser is incident. For example, if thegap distance between the nozzle 502 and the substrate 501 is to be aboutas 40 μm, the light receiving unit 508B is set such that the laserreflected from the substrate 501 is made incident at the center of thelight receiving unit 508B. Accordingly, when the nozzle 502 is too closeto the substrate 501, the laser reflected from the substrate 501 is madeincident at an upper end of the light receiving unit 508B. Then, thevertical driving stepping motor 505 is controlled by the control unit509 to raise the body 504 so that the laser reflected from the substrate501 may be made incident at the center of the light receiving unit 508B.On the other hand, if the nozzle 502 is too far away from the substrate501 so as to cause the laser reflected from the substrate 501 to beincident at a lower end of the light receiving unit 508B, the controlunit 509 lowers the body 504 so that the laser reflected from thesubstrate 501 may be made incident at the center of the light receivingunit 508B. Thus, the gap distance between the nozzle 502 and thesubstrate 501 can be consistently set and maintained at about 40 μm.

After the gap distance between the substrate 501 and the nozzle 502 iscontrolled to be at a desired gap, either the table 500, on which thesubstrate 501 has been loaded, or the body 504, in which the syringe 503mounted therein, is horizontally moved to change position while thesealant is being applied to the substrate 501 to form a seal pattern onthe substrate 501. In the case that the body 504 having the syringe 503mounted therein is moved, a foreign material may be generated due to themovement of the dispenser that can be adsorbed into the substrate 501.Thus, the table 500 with the substrate 501 loaded thereon may be movedin forward/backward and left/right directions to form the seal pattern.The control unit 509 can maintain the desired gap distance as the tableis moved base upon an output from the second sensor 508.

According to the dispenser for a liquid crystal display panel and themethod for controlling the gap between the nozzle and the substrate inaccordance with the present invention, the laser is irradiated forreception by the second sensor while the seal pattern is being formed byhorizontally moving the table 500 with the substrate 501 loaded thereonin the forward/backward and left/right directions. Thus, the gapdistance between the nozzle 502 and the substrate 501 can be controlledor maintained on a real time basis. Even if there is a small unevenportion in the surface of the substrate 501, the seal pattern can stillbe formed with a uniform height and width because of the real timecontrol of the gap distance between the nozzle 502 and the substrate501.

The method for controlling a gap distance between the substrate and thenozzle in accordance with the present invention is started with adriving instruction being input from a user through an input unit suchas a touch panel or a keyboard. In the alternative, the process canstart when a substrate is detected via other types of input devices. Thevertical driving stepping motor 505 automatically lowers the body 504after the input is received. Then, the contact of the nozzle 502 to thesubstrate 501 is detected by the first sensor 507. The body 504 israised by the vertical driving stepping motor 505 and is controlled tobe maintained at a predetermined distance from the substrate 501 basedupon an output from the second sensor 508 such that the gap distancebetween the substrate 501 and the nozzle 502 is consistently and/orconstantly controlled to be at a desired gap distance.

Degradation of picture quality and yield of the liquid crystal displaypanel due to a defective seal pattern can be prevented by using thedispenser for a liquid crystal display panel and the method forcontrolling a gap distance between the substrate and the nozzle inaccordance with the present invention. In addition, even an unskilleduser can precisely set and control the gap distance between thesubstrate 501 and the nozzle 502 in a short time period so thatproductivity is improved.

The shape of the seal pattern formed according to the present inventionmay be varied depending on the method of forming a liquid crystal layer.The method for forming the liquid crystal layer may be divided into avacuum injection method and a dropping method, which will now bedescribed in detail. First, the vacuum injection method begins with aunit liquid crystal display panel having a liquid crystal injectionopening being separated from a large-scale mother substrate andpositioned in a container filled with liquid crystal in a vacuumchamber. Then, liquid crystal is injected into the liquid crystaldisplay panel according to a pressure difference between an inner sideand an outer side of the liquid crystal display panel by varying avacuum degree. After the liquid crystal is filled into the liquidcrystal display panel, the liquid crystal injection opening is sealed toform the liquid crystal layer of the liquid crystal display panel. Theliquid crystal injection opening in the vacuum injection method isdefined as a region opened at each side of the seal patterns. Thus, inthe case of forming a liquid crystal layer at the liquid crystal displaypanel through the vacuum injection method, the seal patterns are formedwith each opened portion to function as a liquid crystal injectionopening.

The vacuum injection method has the following problems. First, it takesa long time to fill liquid crystal into the liquid crystal display panelusing the vacuum injection method. In general, the attached liquidcrystal display panel with an area of several hundreds cm² has only agap of a few μm. Thus, even with the vacuum injection method, which usesthe pressure difference, the injection quantity of liquid crystal byunit time is naturally quite small. For instance, in the case offabricating a liquid crystal display panel of about 15 inches, 8 hoursare required to fill it with liquid crystal. Such a long time taken forfabrication of the liquid crystal display panel degrades productivity.As the size of liquid crystal display panel increase, the time requiredfor filling liquid increases such that productivity further degrades.Therefore, the vacuum injection method does not readily cope with thefabrication of large-scale liquid crystal display panels.

Second, a lot of liquid crystal is consumed using the vacuum injectionmethod. In general, the actual injected quantity of liquid crystal isvery small compared to the amount of liquid crystal filled into thecontainer. Liquid crystal degrades when exposed to air or to a specificgas. Thus, a large amount of liquid crystal remaining after filling hasto be discarded, which increases the unit price of the liquid crystaldisplay device so that price competitiveness of the product is weakened.

In order to overcome such problems of the vacuum injection method, thedropping method has been recently adopted. The dropping method is whenliquid crystal is dispensed by dropping onto one of a large-scale mothersubstrate on which a plurality of thin film transistor array substratesare fabricated or onto another large-scale mother substrate on whichcolor filter substrates is fabricated, and then the two mothersubstrates are attached to each other so that liquid crystal isuniformly distributed at the entire image display regions by theattaching pressure so as to form the liquid crystal layer. Unlike thevacuum injection method, the dropping method then proceeds withattaching the two mother substrates and separating unit liquid crystaldisplay panels from the attached two mother substrates after the liquidcrystal layer is formed.

Because liquid crystal is dropped directly onto the substrate, ratherthan being filled from outside, the seal patterns are formed in a closedpattern encompassing each outer edge of the image display parts toprevent leakage of liquid crystal to the outside. By using the droppingmethod, liquid crystal may be dropped within a short time compared tothe vacuum injection method, and even though the liquid crystal displaypanel is large in size, the liquid crystal layer may be formed quickly.Price competitiveness is strengthened because the unit price of theliquid crystal display panel decreases compared to using the vacuuminjection method since only the required amount of liquid crystal isdropped onto the substrate and thus the high-priced liquid crystal isnot discarded.

Unlike the vacuum injection method, the dropping method proceeds withseparating the unit liquid crystal panels from the large-scale mothersubstrate after the liquid crystal layer is formed. In embodiments ofthe present invention as described above, the seal pattern is formed onthe substrate 501 using a syringe 503 filled with the sealant. However,the dispenser for a liquid crystal display panel and the method forcontrolling the gap between the nozzle and the substrate in accordancewith the present invention can be used for dropping liquid crystal onthe substrate through the dropping method. As discussed above, thedispenser for the liquid crystal display panel in accordance withembodiments of the present invention maintains a gap distance betweenthe nozzle 502 provided at an end of the syringe 503 and the substrate501 is precisely controlled while dispensing material from the syringe503. In the case of dispensing liquid crystal, the syringe 503 is filledwith liquid crystal and a gap between the nozzle 502 and the substrate501 is precisely controlled while the body 504 is repositioned to dropliquid crystal at predetermined positions on the substrate 501.

In addition, the dispenser for a liquid crystal display panel and themethod of controlling a gap distance between a nozzle and a substrate inaccordance with the present invention can also be used in the formationof a silver (Ag) dot during the fabrication of a liquid crystal displaypanel. The Ag dot will now be described in detail with reference to FIG.9, which is a schematic view showing a sectional structure of one edgeof the liquid crystal display panel. As shown in FIG. 9, a liquidcrystal panel is formed such that a thin film transistor array substrate601 and a color filter substrate 602 are attached in a facing mannerwith a certain gap distance maintained by a spacer 603 and a sealpattern 604. The liquid crystal layer 605 is formed in the gap distancebetween the thin film transistor array substrate 601 and the colorfilter substrate 602.

The thin film transistor array substrate 601 is formed with a protrusionand an image display part. In the protrusion part, a gate pad partconnected to gate lines of the thin film transistor array substrate 601and a data pad part connected to data lines of the thin film transistorarray substrate 601 are formed. In the image display part of the thinfilm transistor array substrate 601, the gate lines to which a scansignal is applied through the gate pad part and the data lines to whichimage information is applied through the data pad part are arranged tocross each other, and a thin film transistor for switching the liquidcrystal cells is formed at the crossing. Further, a pixel electrodeconnected to the thin film transistor is formed at the image displaypart of the thin film transistor array substrate 601.

In the image display part of the color filter substrate 602, there areprovided color filters separately formed at the cell regions by a blackmatrix. A common transparent electrode for driving the liquid crystallayer together with the pixel electrode is also formed on the thin filmtransistor array substrate 601. A common voltage line 607 for applying acommon voltage to the common electrode 606 on the color filter substrate602 is formed on the thin film transistor array substrate 601. An Ag dot608 is formed either on the thin film transistor array substrate 601 orthe color filter substrate 602 to electrically connect the commonvoltage line 607 and the common electrode 606 so that the common voltageapplied to the common voltage line 607 may be applied to the commonelectrode 606 by way of the Ag dot 608. At least one or more Ag dots 608can be formed in each of the plurality of unit liquid crystal displaypanels fabricated on the large-scale mother substrate by using thedispenser for a liquid crystal display panel in accordance withembodiments of the present invention. More particularly, the syringe 503(shown in FIG. 6) is filled with Ag and a gap between the nozzle 502 andthe substrate 601 is precisely controlled while the body 504 isrepositioned to deposit Ag dots at predetermined positions on thesubstrate 601.

As so far described, the dispenser for a liquid crystal display paneland the method for controlling a gap distance between the substrate andthe nozzle using the dispenser in accordance with the present inventionhas several advantages. For example, the gap distance can be setautomatically with little or no input from the user. Accordingly,reliability is much improved compared to manual operation such thatdegradation of picture quality and yield due to a defective seal patterncan be prevented. In addition, even an unskilled user can preciselycontrol and set the gap distance between the substrate and the nozzle ina short time so that productivity can be remarkably improved. Further,the gap distance between the nozzle and the substrate may be controlledon a real time basis while the seal pattern is being formed. Therefore,even if there is a small unevenness in the surface of the substrate, theseal pattern may be formed with a uniform height and width. Moreover,the time, effort and expense for dropping liquid crystal or forming Agdots can also be reduced because liquid crystal or Ag, as well as thesealant, can be filled into the syringe within the body and dispensed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the dispenser for liquidcrystal display panel and method for controlling gap between substrateand nozzle using the same of the present invention without departingfrom the spirit or scope of the inventions. Thus, it is intended thatthe present invention covers the modifications and variations of thisinvention provided they come within the scope of the appended claims andtheir equivalents.

1-10. (canceled)
 11. A method for controlling a gap between a nozzle anda substrate using a dispenser for a liquid crystal display panel,comprising: lowering a body with a syringe mounted therein using avertical driving stepping motor; detecting whether a nozzle of thesyringe is in contact with a substrate; raising the body; detecting agap distance between the nozzle and the substrate; and controlling thevertical driving stepping motor so that a desired gap distance isobtained between the nozzle and the substrate.
 12. The method of claim11, wherein controlling the vertical driving stepping motor includesobtaining the desired gap distance of about 40 μm.
 13. The method ofclaim 11, further comprising repositioning the body above the substratewhile maintaining the desired gap distance between the body and thesubstrate.
 14. The method of claim 11, wherein raising the body includesraising the body when the nozzle is detected to be in contact with thesubstrate.
 15. The method of claim 11, wherein detecting the gapdistance between the nozzle and the substrate includes: irradiatinglight from a light emitting unit mounted on the body onto the substrate;receiving a reflected light from the substrate using a light receivingunit mounted on the body; and determining the gap distance according toa position on a surface of the light receiving unit when the reflectedlight is incident and received.